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Boom Cylinder Seals - Do the cylinders need to be removed to change seals or can they be done in place?

peakbagger

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I have a had a slow drip on my left cylinder since I got my SEE. Its not serious leak so I just wrap the cylinder with an oil absorbent pad. I was doing the greasing routine on the backhoe today and looked at it for awhile and it looked to me that I could remove the snap ring and pull the bucket end of the cylinder off the pivot , then rotate it up and remove the big cylinder nut. I got the snap ring off and almost took the cylinder off the pivot but decided the remove the cylinder nut. It was slow going but I got it unscrewed so 7 of those fine tight threads were exposed but no matter how I turned it and would not come off. I think I am the end of the thread but friction in seals and a slight bit of misalignment is keeping it from coming out. Not sure what was going on. I wanted to use it tomorrow, so I retightened the cylinder nut (also very slow) and put the snap ring back on. I put the "diaper" and its back to leaking.

So for those who have done boom cylinder seals, did you take both ends off and remove the cylinder completely? Anyone successfully do it in place like I tried.

I have a universal cylinder nut wrench for turning the nut. It works but I would be tempted to have friend with milling machine make fixed one instead of universal as getting the pins in the holes and then keeping everything aligned was a PITA.
 

Mogman

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I have a had a slow drip on my left cylinder since I got my SEE. Its not serious leak so I just wrap the cylinder with an oil absorbent pad. I was doing the greasing routine on the backhoe today and looked at it for awhile and it looked to me that I could remove the snap ring and pull the bucket end of the cylinder off the pivot , then rotate it up and remove the big cylinder nut. I got the snap ring off and almost took the cylinder off the pivot but decided the remove the cylinder nut. It was slow going but I got it unscrewed so 7 of those fine tight threads were exposed but no matter how I turned it and would not come off. I think I am the end of the thread but friction in seals and a slight bit of misalignment is keeping it from coming out. Not sure what was going on. I wanted to use it tomorrow, so I retightened the cylinder nut (also very slow) and put the snap ring back on. I put the "diaper" and its back to leaking.

So for those who have done boom cylinder seals, did you take both ends off and remove the cylinder completely? Anyone successfully do it in place like I tried.

I have a universal cylinder nut wrench for turning the nut. It works but I would be tempted to have friend with milling machine make fixed one instead of universal as getting the pins in the holes and then keeping everything aligned was a PITA.
Just about any cylinder can be re-sealed without removing the barrel if you have clearance to work with it.
You do have to break the hose fittings loose so air can get in (and fluid out) and allow you to pull the ram out otherwise it will be hydro-locked.
 

Mogman

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I also forgot, I am not familiar with your boom cylinders but many load carrying cylinders have "checks" built into them to prevent the load from falling if a hose breaks, they would also need to be defeated.
For example my Bobcat has those checks in the boom cylinders and there is a cap crew (allen head) that needs to be backed out a couple turns before the ram will move, I would think all this is in your TMs.
MM
 

peakbagger

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Some notes and observations from my recent rebuild. Yes you can rebuild the boom cylinders in place but there are some tricks. I left the cylinder end bolted up and removed the rod end. One issue is that the play in the rod end where it fits over the pin on the boom is quite tight and trying to slide the rod end off the pin is not possible as the rod end gets at an angle to the pin. The trick is the pin goes all the way through the boom and should "float" . I didnt realize that initially and used a big gear puller to push the pin out of the rod. The pin through the boom eventually moved and the pin came out of the rod end.

Getting the rod and piston out of the cylinder required a power pull tied to the bucket. Even with all the hoses disconnected there is a lot of friction on multiple seals and wipers. The cylinder and rod need to be held up in place when they come apart. It may not be an issue with well worn set of seals but with low hours on mine, they were tight.

I then moved to my shop to work on the seals. The threaded plug at the end of the cylinder needs to slide down the rod so it can be removed. The only thing holding it is a lip seal and wiper but it comes off hard. I used two long Jorgenson pipe clamps and the plug came hard despite trying different lubricants. It does not come off smooth, crank on the clamps and it wll jump forward 1/8 of an inch. One way to reduce this effort would be to extend the rod with the hydraulics after its clear of the pin on the boom but that means waiting on unscrewing the plug. IMO, its just another chance to spray hydraulic fluid everywhere.

Getting the big piston bolt (1" grade 8 ) loose requires a lot of torque. I have long 3/4" drive breaker bar and it took all my weight to break it loose. Its a 1-1/8" socket. I doubt a 1/2" drive would work. My 1/2" drive electric impact would not touch it.

Once the piston is off, the plug can be slid off the end of the rod. There are a couple of split guide rings, a wiper seal and the lip seal that have to be inserted in the bore. Getting the lip seal in can be done without a special tool but there is one that shrinks its OD by distorting the ring. As I found out, the lip seal needs to face in towards the piston. In my case the original lip seal was reversed to point out towards the teflon wiper seal causing the leak.

Getting the teflon seal on the piston is not easy. Teflon is not that "stretchy" Foxkits has a video using a small tie wrap to coax it on. Once the ring is in place it will need to be compressed back into the groove. I used a method I saw on YouTube, wrap the outer diameter of the teflon with electrical tape and use a screw type hose clamp to clamp it down for several minutes. It worked quite well.

Next thing is to slide the plug back on the rod. Like getting it off, it really does not want to slide. I had some long 3/8" all thread in stock and made up a special plate with hole in it sized so that the plugs smaller diameter end slips in the hole. The two threaded rods then sit parallel to the rod on either side and run to the rod end where there is another cross piece across the end of the rod. By cranking up the nuts on the all thread it slowly slid on a bit at a time. I just needed it to slide on a foot or so.

I cleaned up the big bolt and the threaded hole as well as I could as used electrical contact cleaner to get the threads clean and dry. I used Loctite blue on the threads and used my breaker bar to crank it tight. The tables show 625 ft/lbs of torque for a 1" grade 8. My 3/4" torque wrench does not go up that high so I just applied all my weight on a long breaker bar.

I then slide the rod and piston in and the seals seemed to clear. It took a bit of persuasion to get in in far enough to engage the threads of the plug but eventually I got the plug screwed in.

The last thing to do is get the rod end lined up with pin in the boom. Sounds simple but it was not easy. I started up the SEE and moved the boom lever to move the piston but its not smooth as its not full of oil immediately. Even with the rod end lined up with a cleaned up pin, it did not want to go in. I had to make up another clamp with all thread to push the pin from the other side of the boom into the rod end. Once the set up was in place it went quick.

BTW the snap ring on the pin is very beefy and regular snap ring pliers would have a tough time on them. I got a screw type ring remover on Amazon to get the ring on and off.

The boom cylinder definitely does not move smooth initially but once the boom is slowly exercised it smooths out. I could not stroke it fully as I didnt have a hole to dip into but expect it will need a bit of exercise through its entire range.

So two special tools to buy, the special wrench to unscrew the plug and a two foot 3/4" breaker bar to turn it and the heavy duty snap ring tool. A 3/4" drive breaker bar a minimum of 3 feet long and a 3/4" 1-1/8 socket. I did this solo, if I had unbolted the cylinder and hauled it to a shop to get it rebuilt I would have needed an assistant or a overhead lifting tool.
 
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Mogman

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The part with the seals in it that goes over the rod is called a gland.
I have allot of stuff around the farm with different types of cylinders, some with 2-3 sections, I have a knuckle truck right now with a blown seal, the rod is almost 4" I need to get someone to help me with that one as it is too heavy to do myself.
I just pop off the gland take it and if needed the piston down to the local hydraulic shop and they charge me what I think is a very minor fee to clean the glad up and pop the seals in for me, some need to be heated and they know exactly what needs to be done.
I took a gland from the steering cylinder on my JLG 40F man lift, probably a 1 1/4" rod cylinder a couple weeks ago and it cost me $35.00 that big cylinders gland may cost me $75.00 and they work perfect every time.
If I was to take the complete cylinder it would cost MUCH more because they by law have to test and certify the cylinder and some of my old cylinders would not certify anyway.
 

porkysplace

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Yes they can be done without removing , but it increases the chances of dirt or other contaminant's getting in while rebuilding .
 
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